The present invention relates to the construction of a firebrick member such as nozzles valves, spouts, ladle lips, or the like and particularly to such members made from ceramic sinterable material having passage opening for the delivery of molten metal and feed conduits for the introduction of a treatment gas.
In the casting of metals, vessels such as ladles and tundishes (used in continuous casting procedures) are employed to hold quantities of the molten metal from which a given charge may be caused to flow and be fed in a generally quantatively controlled manner into a suitable mold. The outlet from such vessels or ladles are generally provided with a shaped refractory brick having a passage or duct for the molten metal. Such bricks are made from high-grade, wear-resistant material. These shaped bricks can take many forms, as for example, a ladle or tundish nozzles, immersion nozzles, or parts of sliding gate valves having nozzle bricks, nozzle brick inserts, bottom plates, slide plates and chute nozzles. It is common to all of these brick members that they have a passage opening for the molten metal and therefore at least in the area which comes into contact with the melt during casting, is subject to erosion and damage.
Furthermore, during the pouring of molten metal, particularly steel, there is often a need to treat the melt with a gas immediately before or at the time that it leaves the vessel. For example, inert gases are used to prevent oxides from being deposited in the passage opening or to aid in the separation of oxide particles from the surface of the fire brick. For further example, the feeding of oxygen to the molten metal leads to a more intense boiling of the unkilled melts held in the passage, or to a reburning of the material in a frozen-up spout. In addition to these purely metallurgical effects, such gas treatment can also be used to control the flow of metal, and the casting jet, in the sense that it may be used as a braking or throttling means. In some cases, the introduction of the gas directly into the passage opening of the particular brick has proven merely advantageous; in other cases, it has proven to be unavoidably necessary.
To the foregoing end, it has been known to supply the gas by making the entire brick, or at least that part of the brick in the immediate vicinity of the metal passage opening, from a porous refractory material and thereafter, forcing the gas through the pores under increased pressure. However, this method of supplying the gas has not proven satisfactory because the porous, that is, the gas-permeable material, has inadequate wear resistance. As a result, it fails to meet the service life requirements under normal operating conditions, as occur when molten steel flows along the wall portions of the passage opening.
In Austrian Pat. No. 1,314,114, a firebrick has been suggested which is provided with a passage opening for molten metal and with a plurality of gas ducts passing through the brick and which, at their outer ends, are connected to a feed conduit, and, at their inner ends, issue into the molte passage opening. These gas lines have a constant cross section over their entire length which, when relatively large, allows the molten metal moving through the passage opening to flow into the gas line if the gas pressure is inadequate. This prevents further flowing of the gas. It has, however, heretofore proved impossible, within the framework of firebrick manufacture, to form bricks having gas ducts with a very small diameter, preferably of no more than a few tenths of a millimeter, which would prevent the penetration of the molten metal into the gas duct. Bricks, commonly used, are made from a material containing a high portion of crude carborundum. Due to the high level of hardness of such material, it is impossible to use conventional tools to produce bores in cured or finished burnt bricks having the necessary small diameter for the desired gas lines.
It is the object of the present invention to provide a firebrick of the type described herein, and a method for manufacturing the same, which overcome the disadvantages of the prior art.
It is a further object of the present invention to provide a firebrick for use in the feeding of molten metal, which maintains the requisite wear resistance to the molten metal and permits the introduction of the treatment gas without any danger of the molten metal penetrating into the gas duct.
It is a further object of the present invention to provide an improved method for manufacturing shaped firebrick.
The foregoing objects, together with other objects and advantages, will be apparent from the following disclosure.